Effect of heat treatment on microstructure and densification of oxide dispersion strengthened Fe-Cr alloy

Fe-Cr pre-alloyed powders, pure Ti powders and nano Y₂O₃ powders were processed by mechanical alloying (MA), and then the as-milled powders were sintered by hot isostatic pressing (HIP). Different heat treatment processes were conducted on the consolidated samples. The microstructure evolution was investigated by XRD, SEM and TEM. Voids resulted from MA are remained in matrix during HIP, but the initial morphology is changed, and the regular small voids instead of irregular large voids are distributed homogeneously. Voids are linked up each other and developed into larger voids after annealing at 1 100 ℃ for 5 h. TEM images indicate that grain coarsening is occurred with the increasing normalizing temperature, while the microhardness is decreased sharply until 1 050 ℃.